Process and apparatus for making a leakproof plastic container by completely ejecting from a mold and transferring to a cap closing station

ABSTRACT

A process and apparatus for forming a leakproof plastic container by completely ejecting from a mold and then transferring to a cap closing station. The process includes the steps of injecting a molten plastic material into a mold cavity and then opening the mold and ejecting the body and cap completely from the mold. Subsequently, the body and cap are gravity fed to a collection device and then transferred to a cap closing station. In the cap closing station, the body and cap are sealed before the material is fully set to form a leakproof seal.

FIELD OF THE INVENTION

[0001] The present invention relates to an apparatus and process forforming a leakproof seal between a cap and a body of a container afterthe container is completely ejected from a mold and then transferred toa cap closing station.

BACKGROUND OF THE INVENTION

[0002] A plastic body and cap of the type to which the present inventionrelates is generally an injection-molded plastic container that has aplastic cap adapted to seal the body closed with a leakproof seal. Suchbody and cap are, for example, the vial that may be used to collect atest sample of milk or urine, or to ship sterile water, or other typesof containers having caps. The cap is typically integrally connected tothe body.

[0003] U.S. Pat. No. 4,783,056 relates to a method for accomplishingsealing of a cap onto a vial including a mold with several moving partsin which the vial may be molded and sealed in the same apparatus. Thismethod of forming and sealing an aseptic vial eliminate the additionalstep of sealing the vial under aseptic conditions because the sealing isdone directly in the mold while the vial is still hot enough to maintainthe necessary pliability and sterility of the vial. However, this methodrequires the use of a mold which has moving parts for closing andsealing the cap on the vial and does not easily facilitate the transferof a liquid to the container prior to sealing.

[0004] U.S. Pat. No. 5,723,085 relates to a process and apparatus formaking a leakproof cap and body assembly. This process discloses amethod of injecting a molten material into a mold cavity, separating themold cavity, engaging at least the body with a robotic arm while theassembly is in the mold and moving the cap and body assembly with therobotic arm into a capping device while the body and cap are at atemperature at which the material is not fully set. The body is thensealed by moving the cap into engagement with the body to form aleakproof seal.

SUMMARY OF THE INVENTION

[0005] The present invention relates to a process and apparatus formaking a leakproof plastic container. The process relates to a processfor forming and sealing a cap onto a body with a leakproof seal afterthe body and cap assembly are completely ejected from a mold, and thebody and cap assembly are transferred to a cap closing station.

[0006] More specifically, a more complete appreciation of the presentinvention and many of the attendant advantages thereof will be readilyunderstood by reference to the following description when considered inconnection with the accompanying drawings within.

BRIEF DESCRIPTION OF DRAWINGS

[0007]FIG. 1 is a top view of one embodiment of the present inventionshowing a hopper, conveyor and a cap closing station.

[0008]FIG. 2 is a top view of one embodiment of the present inventionshowing a cap closing station.

[0009]FIG. 3 is a side view, in a partial cross section of oneembodiment of mold of the present invention;

[0010]FIG. 4 is a cross-sectional view of one embodiment of a body andcap of the present invention.

[0011] Among those benefits and improvements that have been disclosed,other objects and advantages of this invention will become apparent fromthe following description taken in conjunction with the accompanyingdrawings. The drawings constitute a part of this specification andinclude exemplary embodiments of the present invention and illustratevarious objects and features thereof.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0012] The present invention relates to a process and apparatus formaking a leakproof plastic body and cap. The term “leakproof” means thatthe body and cap (i.e., the container) passes the blue crystal dye test.The blue crystal dye test is a visual test to detect leaks between thebody and cap. A container “passes” the blue crystal dye test if thewhite paper, in which the container is placed on, does not visuallychange color (i.e. The white paper does not become contaminated with theblue crystal dye liquid from the container). The blue crystal dye testprocedure consists of the following: (a) the blue crystal dye liquid isprepared by adding one teaspoon of blue crystal dye powder to one gallonof alcohol and then throughly mixing the solution; (b) the blue crystaldye liquid is poured into the container (i.e. a sufficient amount of thedye liquid must be added so, when the container is placed upside down,the entire seal area must be covered); (c) the container is closed byapplying, sufficient downward pressure on the cap to completely andevenly seat the cap on the body; (d) the container is placed upside down(i.e. inverted) on the white paper at room temperature; and (e) after 4hours, the white paper is inspected to determine if the white paper iscontaminated with the blue crystal dye liquid.

[0013] The phrase “not fully set” means that: 1) the plastic materialforming the body and cap are at a temperature between the glasstransition temperature (Tg) and the melting point (Tm) of the material;2) the cap and body are rigid enough to retain their shape and be movedwithout damage; and 3) the sealing surfaces on the cap and body are warmenough to conform to each other to make the required leakproof seal, yetcool enough so that the cap can be opened and closed without sticking.The glass transition temperature (Tg) is the point below which plasticbehaves as glass does. Below Tg, the thermoplastic will be very strong,fully rigid (or fully set), and brittle. At or above Tg, the plastic isnot as strong or rigid as glass, and is not brittle. And finally, aboveTm, the plastic is a fluid melt. Tg and Tm values are widely publishedfor commercial plastic materials, and typically appear in texts onplastic materials. For example, as reported in the Polymer Handbook,2^(nd) Edition. J. Wiley (1975) at V-24, the Tg of polypropylene islisted at −18° C. (0.4° F.), with the Tm at +171° C. (+340° F.). Thevial temperature may be measured either on the sealing surface of thevial (assuming sufficient pyrometer contact area), or on the outersidewall of the vial near the sealing surface to ensure sufficientpyrometer contact area.

[0014] The apparatus and process of the present invention can be used tomake a variety of bodies including bottles, vials, spouts or any othercontainer requiring a leakproof seal. The invention will be described inthe drawings and description with respect to a vial. However, it shouldbe understood that the process and apparatus of the invention appliesequally to any container requiring a leakproof plastic seal and, assuch, is not limited to vials.

[0015] As an illustrative example, the vial 16, as shown in FIGS. 3 and4, may be cylindrical in shape with an integrally formed bottom. A cap18 is provided which, when closed, forms a leakproof seal. In oneembodiment, the cap 18 is integrally connected to the vial 16 with asmall flange 20. The vial 16 and cap 18 may be injection molded in amold 10. Suitable material for the body and cap includes plastic (e.g.thermoplastics such as polyethylene and polypropylene). In anotherembodiment, the cap 18 includes a circular, flat center portion 22having a rim 24 extending perpendicularly from the outer edge thereof.The rim is intended to fit over the upper edge of the outer wall of thevial in a sealing manner.

[0016] The vial 16 and cap 18 are injection molded using anyconventional design known in the art that forms a plastic moldedarticle. In one embodiment of an injection molding process, as partiallyillustrated in FIG. 3, the end, intermediate and stripper plates 32, 34,35 are held against the frame of the mold 10 with about 15 fifteen tonsof pressure by a press means (not shown). Molten plastic is theninjected through the sprue gate 106 with about fifteen tons of pressureso as to form the vial 16 and cap 18. In an illustrative embodiment, theinjected vials are allowed to cool for about six seconds while thetemperature thereof drops from about 550° F. to about 100°-120° F. Thespecific temperature to which the vial 16 is formed and the time, priorto opening the mold, is dependent on numerous factors including the typeof plastic, and size and type of vial but should be cool enough so thatthe plastic will retain its shape, and hot enough so that the plastic isnot fully set. In one embodiment, water is circulated through the waterchannels 96, 100, 102 of the mold 10 in order to accelerate the coolingof the vial 16 and cap 18.

[0017] In another embodiment, when the vial 16 and the cap 18 aresufficiently cooled, the end plate 32 and the intermediate plate 34 arewithdrawn from the frame 40 of the mold 10. As described above, as theend and intermediate plates 32, 34 initially move away from the frame40, the spring 52 acts between the stripper plate 36 and the end plate32 to hold the stripper plate 36 against the frame 40. After the end andintermediate plates 32, 34 have separated from the stripper plate 36 byabout one inch, the head 44 of the bolt 42 engages with the shoulder 48of the chamber 46 within the end and intermediate plates 32,34 and pullsthe stripper plate 36 away from the frame 40. The rods 54 are guidedwithin their respective openings 56 and bores 58 to maintain the threeplates 32,34,36 in alignment with the frame 40 during the separation ofthe plates 32,34,36 from the frame 40. The first and second cores 60,72, being attached to the intermediate plate 34, move away from theframe 40 together with the plates 32, 34, 36.

[0018] In a particular embodiment, the plates 32,34,36 and the frame aremounted on parallel rails (not shown) so that they remain in an alignedrelationship even when the mold is opened. The vial is then ejected fromthe mold using any conventional design known in the art that completelyremoves the vial from the mold without incurring damage to either thebody or cap. In one embodiment, a jet of air drives an air poppetthrough its housing until it contacts the vial and pushes it from themold. When the air poppet is projected into the mold cavity, aircurrents that drive the air poppet may further assist in ejecting thevial. The air poppet may be provided with an angled surface that willcontact the vial in a flat manner so as not to mark the vial. In anotherexample, a mechanical pusher may be employed to contact the vial andpush it out of the mold. In a further example, an ejector sleeve may beemployed to push the vial out of the mold.

[0019] When the vial 12 and cap 14 have been ejected, the plates arereturned to the mold by the press to close the mold, and additionalplastic is injected into the mold to repeat the cycle.

[0020] Although the invention has been described with respect to aparticular mold, it should be recognized that other types of molds couldbe used to form the bodies and caps according to the invention. Forexample, in the present invention, the process and apparatuses forseparating the mold may encompass either the instance where: (a) the capand vial remain engaged to the female mold part; or (b) the cap and vialremain engaged to the male mold part. As another example, the moldcavity and core may be modified to still accomplish the injectionmolding process.

[0021] With reference to FIG. 1, one embodiment of the present inventionincludes a hopper 200 for collecting the body and cap that is ejectedfrom the mold, a transfer device 300 for transferring the body and capfrom the hopper to the cap closing station 400 and a cap closing station400 for sealing the cap to the body.

[0022] After the vial 16 is completely ejected from the mold, the vial16 communicates with a transfer device 300. In one embodiment of themethod of communicating with the transfer device as shown in FIG. 1, thevial 16 is gravity fed to a collection device 200 such as a hopper thatis connected to the transfer device 300. Such methods of gravity feedingmay include directly dropping the vial 16 and cap 18 into a collectiondevice, or a chute or a conveyor that directs the vial 16 to thecollection device or to the transfer device 300. To assist in thedirection of the vial 16, the chute or conveyor may also include anadditional mechanical device such as a belt, or air pneumatics. Inanother embodiment, the vial 16 may be ejected out of the mold 10directly into a collection device 200 such as a hopper or other types ofcontainer that collects one or more vials that is located below themold.

[0023] The transfer device 300 may be any device that is used to movethe body and cap to the cap closing station. Examples of such transferdevices include belts, rollers, conveyors, apron conveyors, vibratorconveyors, oscillating conveyors, pneumatic conveyors, and rollconveyors. The only limitation as to the configuration of the transferdevice is that the device does not damage the sealing surface of thebody and cap.

[0024] In one embodiment, as partially shown in FIG. 1, the vial 16 iscorrectly oriented in the transfer device 300 by rollers 310 on eachside of the vial 16. For example, the rollers may be: (a) two flatcylinders that are parallel to each other; (b) spaced apart a distanceapproximately equal to the diameter of the vial; (c) set on a declinefrom the hopper to the cap closing station; and (d) rotated so that oneroller is rotating in the clockwise direction and the other rollerrotating in the counter-clockwise position. As such, the vial 16 isdischarged from the bottom of the hopper 200 and the rollers 310 on eachside of the vial 16 rotate to both correctly orient the vial 16 with thebody in the upright position (the cap is properly oriented in theloading position of the cap closing station) and to move the vial 16from the hopper 200 to the cap closing station 400. In a more specificembodiment, hopper 200 is designed to vibrate so that one or more vialswill freely flow out of the hopper. The configuration of the hopper 200,the transfer device 300 and the cap closing station 400, as shown inFIG. 1, is for illustration purposes, and thus other configurations maybe used without departing from the scope of the invention.

[0025] In order to provide a seal between the cap and the vial which isleakproof, the cap 18 must be mated with the vial rim 26 when theplastic is not fully set. The sealing of the cap to the vial while theplastic is not fully set allows the cap and vial to conform to eachother and to form the required leakproof seal. However, the cap cannotbe placed on the vial until the plastic has cooled enough so that thecap and vial will not melt into one another. Sealing of the cap too soonwill cause the cap to be permanently fixed and unremovable. It isnecessary to remove the vial from the mold and move it to the capclosing station within a particular window of time while to the plasticis not fully set. This window of time will vary for different materials,and different sizes and shapes of containers. For example, in oneembodiment, the amount of time before the material is not fully set maybe in the range of about 1 to about 10 minutes.

[0026] The cap closing station 14, as illustrated in FIG. 2, is used toclose the cap 18 onto the vial 16 within the window of time where theplastic is not fully set. In the embodiment shown in FIG. 2, the openvial (body 16 and cap 18) is transferred to the loading position 410where the vial is correctly oriented in the loading position 410.Gripper jaws 415 and 420 lock the vial 16 into place. Sufficient forceis exerted by the gripper jaws 415, 420 on the vial 16 to hold the vial16 in place while vial 16 is horizontally moved to the cap closingposition 490 but, at the same time, the force on the vial must beregulated so as to avoid causing damage to the body 16 and cap 18 of thevial. Open vial 16 and cap 18 are moved from position 410 to position490 by a slide 450. While vial 16 moves horizontally from position 410to position 490, cap 18 slides over passive guide 425 that causes cap 18to move from a fully open position (shown in FIG. 4) to a substantiallyclosed position by flexing the flange at point 21 (of FIG. 4) thatconnects the cap to the body so as to ensure the proper alignment of thecap on the upper edge 26 (of FIG. 4) of the body. Once vial 16 andlocated at position 490, cylinder 480 (which is directly above vial 16and located at position 490) is actuated to contact the outside surfaceof the cap and to apply sufficient downward force on the cap tocompletely and evenly seal the cap to the body. Subsequently, cylinder480 backs-off of contacting the surface of the cap. Gripper 415 and 420open and the sealed vial is discharged from the cap closing station atposition 500. Suitable methods of discharging the sealed vial from thecap closing station include, but are not limited to, a flipper, lever,mechanical pusher or controlled air jets.

[0027] In another embodiment, cylinder 480 may be a flipper or othermechanical devices that applies sufficient downward pressure on theoutside surface of the cap to seat completely and evenly the cap to thebody. In yet another embodiment, gripper jaws 415, 420 may also be otherdevices that apply sufficient force to lock the body but does not causedeformation to the body or cap or otherwise puncture the body.

[0028] In a further embodiment, the passive guide 425 (which does notmove) may also be an “active” guide that moves to assist in properflexing the flange at point 21 so that the cap moves from a fully openposition to a substantially closed position.

[0029] In another embodiment of the cap closing station 400, the bodyand cap is locked into a stationary position and a rotary flipper orcomparable device moves the cap from the open position to the closed andsealed position and ensures that the flange properly flexes at point 21so that proper alignment is maintained when the cap contacts the upperedge 26 of the body and then subsequently applies downward force on theoutside surface of the cap to completely and evenly seat the cap on thebody.

[0030] In a further embodiment where the upper portion of the body islocked in the cap closing station, the flange connecting the cap to thebody may be flexed (e.g. pivoted) so as to bend the flange at point 21prior to entering the cap closing station. By doing so, the proper bendin the flange is maintained while the body and cap proceeds along thepassive guide 425 of the cap closing station from point 410 to point490. In another embodiment, the body is locked at two locations withinthe cap closing station 400—at the bottom of the vial and at the upperportion of the body (i.e. below the sealing surface). In this way, asufficient amount of force may be exerted at the bottom of the body tolock the body into the cap closing station without causing deformationto the body. Consequently, sufficient force need only be exerted at theupper portion of the body to maintain alignment of the vial through thepassive guide from point 410 to point 490 without causing anydeformation to the body. In one embodiment, the operation of the gripper415, 420, slide 450 and cap closing device 480 may be operated bypneumatic cylinders (not shown). However, it should be recognized that amechanical mechanism could also be used to operate these devices.

[0031] In one embodiment, after the cap is closed in the cap closingstation, a conveyor for transporting cartons is positioned below the capclosing station so that the sealed vials may be dropped directly intothe cartons. For example, the vial may be ejected from the cap closingstation in response to a signal from the sensor, to drop the sealed vialinto the awaiting carton.

[0032] In yet another embodiment of the design of the cap and vial asshown in FIG. 4, a seal 82 and the cap rim 90 combine to form an annularregion for interlocking with the vial 16. However, the present inventionis not limited to the design detailed in FIG. 4 and thus, may includevarious modifications of the seal design. Consequently, specificdimensions used throughout this specification are exemplary and are onlyintended to illustrate relative sizes of the various elements and not inany way to limit the present invention to the particular discloseddimension or operating parameters.

[0033] The present invention will be illustrated in greater detail bythe following example. It is understood that this example is given byway of illustration and is not meant to limit the disclosure or claims.The following example illustrates that, surprisingly, it has now beenfound that the body 16 and cap 18 may be ejected fully and completelyfrom the mold 10 and gravity fed to a transfer device without affectingthe subsequent ability to form a leakproof seal so long as: (a) the bodyand cap is closed before the material is fully set; and (b) the sealingsurface of the body and cap are not damaged. Specifically, afterinjection molding, polypropylene were ejected from the mold and allowedto free fall from the mold to a carton (approximately 2 feet below themold). The flange connecting the cap to the body of each vial was thenflexed at point 21. Each vial was then placed in the closing devicedetailed above, and the cap was sealed to the body. Tests were conductedon vials that were sealed at 15 seconds, 30 seconds, 2 minutes and 10minutes, measured from the time the vial was ejected from the mold.Surprisingly, each and every vial was found to be leakproof.

[0034] While the invention has been described in detail with referenceto specific embodiments thereof, it will be apparent to one skilled inthe art that various changes and modification can be made, andequivalents employed, without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A process for forming a leakproof plasticcontainer comprising the steps of: (a) injecting a molten plasticmaterial into a mold cavity to form a molten body and cap; (b) openingthe mold cavity; (c) ejecting the body and cap completely from the moldbefore the material is fully set; (d) communicating the body and capwith a transfer device; (e) transferring the body and cap with thetransfer device to a cap closing station; and (f) sealing the cap to thebody in the cap closing station before the material is fully set to forma leakproof seal.
 2. An apparatus for forming a leakproof plasticcontainer comprising: a mold having a mold cavity; a device forinjecting a molten plastic into the mold cavity to form a body and acap; a device for opening the mold; an ejecting device cooperating withthe mold opening structure to completely eject the body and cap from themold before the material is fully set and without causing damage to thesealing surfaces on the body or cap; a transfer device for transferringthe body and cap to a cap closing station after the body and cap havebeen completely ejected from the mold, wherein the transfer device isconfigured to move the body and cap without incurring damage to eitherthe body or cap; and a cap closing station to seal the cap to the bodywhile the body and cap are not fully set to form a leakproof seal.
 3. Aprocess for forming a leakproof plastic comprising the steps of: (a)injecting a molten plastic material into a mold cavity to form a moltenbody and cap; (b) opening the mold cavity; (c) ejecting the body and capcompletely from the mold before the material is fully set; (d) gravityfeeding the body and cap into a collection device; (e) transferring thebody and cap with a transfer device from the collection device to a capclosing station; and (f) sealing the cap to the body in the cap closingstation before the material is fully set to form a leakproof seal.
 4. Anapparatus for forming a leakproof plastic container comprising: a moldhaving a mold cavity; a device for injecting a molten plastic into amold cavity to form a body and a cap; a device for opening the mold; anejecting device cooperating with the mold opening structure tocompletely eject the body and cap from the mold before the material isfully set and without causing damage to the sealing surfaces on the bodyor cap; a collection device for receiving the body and cap that isgravity fed from the mold and for containing at least one body and cap;a transfer device for transferring the body and cap from the collectiondevice to a cap closing station, wherein the transfer device isconfigured to move the body and cap without incurring damage to thesealing surfaces on the body or cap; and a cap closing station to sealthe cap to the body while the body and cap are not fully set to form aleakproof seal.